Contour plot of eccentricity versus true anomaly during the mid-transit (φ). For a circular system (e = 0) the density should equal ϱ_o ⋍ 2.6 g/cm³, as can be calculated for the given values of R_⋆ and M_⋆. The TBD derived from the a/R_⋆ values of ϱ_⋆ for the planets Kepler-210b (black line) and Kepler-210c (gray line) can be explained for eccentricities ≳0.4 and ≳0.51 respectively, depending on the true anomaly of the planet during the mid-transit. The dashed lines represent the uncertainty limits.